Curable copolymers of tetrafluoroethylene



United States Patent 3,366,879 CURABLE COPOLYMERS OF TETRA- FLUORGETHYLENE Dexter l3. Pattison, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, Dei., a corporation of Deiaware No Drawing. Filed June 25, 1962, Ser. No. 205,112 18 Claims. (Cl. 26077.5)

This invention relates to a novel elastomeric copolymer. More particularly this invention relates to curable, fluoline-containing elastomeric copolymers.

Elastomers prepared from certain fluorine-containing monomers have become well-known for their outstanding properties. For example, copolymers containing, by weight, 70-36% of vinylidene fluoride and 30-70% of hexafiuoropropene are elastomers of superior properties where resistance to hi h temperatures and to attack by hydrocarbon solvents is important. Copolymers containing units of vinylidene fluoride, hexafiuoropropene, and tetrafiuoroethylene in certain proportions are significantly superior in some respects to the polymers containing only vinylidene fluoride and hexafluoropropene units. The search continues, however, for additional elastomeric materials which are significantly superior in one or more properties, and which at the same time are economically attractive.

It is an object of this invention to provide novel fluorine-containing elastomeric copolymers. Another object is to provide new elastomen'c copolymers which show excellent electrical insulation properties and good combined resistance to the effects of light, heat and chemicais.

A still further object is to provide novel elastomeric copolymers from relatively inexpensive monomers which copolymer combines the aforementioned properties. Other objects will appear hereinafter.

These and other objects of this invention are accomplished by providing a curable elastomeric copolymer comprising (a) about 45 to 55 mole percent of -CF CF uni-ts, (b) about 54.8 to 35 mole percent of (IJH-OH2 units and (c) about 0.2 to mole percent of (I3HOH2 OCHz-CH2X units wherein R is a saturated aliphatic hydrocarbon radical containing 1 to 18 carbon atoms or a radical wherein R is a saturated aliphatic hydrocarbon radical containing 1 to 4 carbon atoms and X is a halogen radical of an atomic number of 17 to 53 (chlorine, bromine and iodine), the hydroxyl group or a radical of the structure where Y is hydrogen or a saturated aliphatic hydrocarbon radical containing 1 to 8 carbon atoms. It is to be understood that R in the (b) units need not be the same in the copolymer.

The presence of the tetrafluoroethylene units is an essential feature of this invention. Copolymers in which part or all of the tetrafiuoroethylene units are replaced by units derived from other halogen-containing olefins, such as chlorotrifiuoroethylene and hexafiuoropropene, have poorer low-temperature properties and tend to be plastics at room temperature. It has been found that in copolymerizing tetrafiuoroethylene with the comonomers providing the (b) and (c) units, the tetrafiuoroethylene units are usually incorporated in an amount corresponding to approximately one mole of tetrafluoroethylene units to a total of one mole of the units (b) plus (0). The units (0) corresponding to the formula CHCHT- (|)CH2CH2X are essential to provide cure sites. If less than 0.2 mole percent of these units is present in the copolymer, the copolymer cannot be satisfactorily cured. On the other hand, if more than 10 mole percent of these units is present, the cost of the copolymer is increased, the thennal stability is usually inferior, and the elongation at break of the cured vulcanized elastomers tends to be undesirably low. The preferred proportions of (-c) units is in the range of about 0.5 to 4 mole percent.

Examples of suitable monomers giving the (b) units of the above definition are methyl vinyl ether, ethyl Vinyl ether, propyl vinyl ether, isopropyl vinyl ether, the various isomeric butyl vinyl ethers, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, n-hexadecyl vinyl ether, n-octadecyl vinyl ether, 1-isobutyl-3,S-dimethylhexyl vinyl ether, 2- methoxyethyl vinyl ether, and 2-butoxyethyl vinyl ether. Mixtures of any of these monomers may be used. The preferred monomer is methyl vinyl ether because the copolymers prepared with this monomer in general show the most desirable properties. When the polymer contains, as the (b) component, both methyl vinyl ether units and units of an alkyl vinyl ether in which the alkyl group contains at least 3 carbon atoms, the vcopolymer shows improved low-temperature properties with some sacrifice in high-temperature stability. The preferred molar proportion of these higher alkyl vinyl other units in the polymer is about 5 to 20 mole percent, based on the total molar amount of the (b) component present in the copolymer.

Examples of monomers which give (c) units of the above definition are 2-chloroethyl vinyl ether, 2-bromoethyl vinyl ether, 2-iodoethyl vinyl ether, 2-formamidoethyl vinyl ether, Z-acetamidoethyl vinyl ether, 2-octanoylaminoethyl vinyl ether, and Z-hydroxyethyl vinyl ether. The preferred comonomers are the chloroethyl, bromoethyl, and iodethyl vinyl others, the chloroethyl vinyl other being most preferred.

The copolymers of this invention are prepared by copolymerizing a mixture of monomers using known tech niques. The polymerization may be carried out in bulk or in the presence of an inert diluent such as water or an organic solvent. Examples of suitable organic solvents are keto'nes such as acetone and methyl ethyl ketone, esters such as butyl acetate and ethyl acetate, and alcohols such as isopropyl alcohol and tertiary butyl alcohol. Tertiary butyl alcohol is the preferred organic solvent for obtaining high-molecular weight polymers.

When using an aqueous medium it is helpful to use an emulsifying agent such as the alkali metal salts or ammonium salt of a long-chain alkyl sulfate. The use of an emulsifying agent is necessary if it is desired to obtain the copolymers in the form of a stable latex. The emulsifying agent should be used in amounts ranging from about 0.05 to about 5.0 percent by weight, based on the amount of monomers used in the polymerization. Other suitable emulsifying agents include the alkali metal or ammonium salts of long-chain fluorinated fatty acids, saturated fatty acids, or rosin acids. Specific examples are ammonium perfluoroctanoate, potassium stearate, and the sodium salt of tetrahydroabietic acid or a disproportionated rosin.

Polymerization is initiated by means of a conventional free-radical polymerization initiator. Well-known types of polymerization initiators are the compounds containing a peroxy group. Examples of these are hydrogen peroxide, benzoyl peroxide, cumene hydroperoxide, and water-soluble salts of persulfuric acid, such as sodium persulfate, potassium persulfate, and ammonium persulfate. Other types of free-radical polymerization initiators which may be used are the azo compounds disclosed in U.S. Patent 2,471,959, such as 2,2'-azobis(2-methylpropionitrile), and nitrogen fluorides. In an aqueous system it is preferred to use one of the persulfates because of their water solubility and ready availability. In an organic solvent such as tertiary butyl alcohol, it is preferred to use 2,2'-azobis(Z-methylpropionitrile). The amount of polymerization initiator used will depend on many factors, including the nature of the initiator, the medium, the temperature, etc. Normally, not less than about 0.001 percent and not more than about percent, based on total weight of monomers, is used. In the preferred systems .using ammonium persulfate or 2,2-azobis(Z-methylpropionitrile), the amount used will range from about 0.05 to about 1 percent.

The polymerization is carried out at moderately elevated temperatures in the range of C. to 150 C. Lower temperatures may be used, but the polymerization will proceed more slowly. Likewise, higher temperatures may be used .with a corresponding increase in polymerization rates. In general, it is preferred to use as low a temperature at which a satisfactory rate of polymerization may be attained to avoid possibly deleterious effects of higher temperatures on the copolymers. Also a low reaction temperature tends to increase the molecular weight of the copolymers. The preferred temperatures range from about C. to about C. v

The pressure used is not critical. Pressures may be as low as p.s.i.g. initially or as high as 50,000 p.s.i.g. In general, the pressures used are those which normally develop in the closed system during the heating of the reaction mixture. The preferred initial pressure is about to 600 p.s.i.g.

The polymerization should be carried out at pI-Is in the range of 7 to 10. If the medium becomes too acidic, hydrolysis of the vinyl ether may occur, and the desired polymerization does not take place.

Alkali metal sulfites or bisulfites may be used if desired with the persulfate catalysts to improve the rate of polymerization. Chain-transfer agents such as alkyl mercaptans, secondary alcohols (e.g., isopropanol) or ketones (e.g., acetone) may be employed in either aqueous or organic solvent systems to give lower-molecular-weight polymers.

The polymerization should be carried out in an inert atmosphere, such as in an atmosphere of nitrogen or argon. The reaction may be carried out in pressure vessels in which the surface exposed to the reaction mass is composed of an inert material such as stainless steel, glass, silver, etc. The polymerization may be carried out by a batch or a continuous process.

The copolymers are isolated by known methods. In a medium in which the polymer is not soluble, the liquid phase may be removed mechanically, and the polymer may then be washed and dried. If the polymer is prepared in latex form, the polymer may be coagulated, for example by freezing or by coagulation with salt, and removed mechanically from the separated liquid phase.

The copolymers of this invention may be used in the uncured state, or they may be compounded, fabricated, and cured in the same way as known fluoroelastomers. The presence in the copolymer of the units defined as (c) above make them even more readily curable than the known fiuoroelastomers. Particularly the copolymers containing the pendant chloroethoxy, the bromoethoxy, or the iodoethoxy groups may be vulcanized by a wide variety of agents developed for other halogen-containing elastomers, such as vinylidene fiuoride-hexafiuoropropene copolymers and the polymers of chloroprene (2chloro- 1,3-butadiene). The curing rate in most recipes increases in the following order: chloro bromo iodo so that a shorter time in the press is required for the copolymers containing iodoethoxy groups, and the postcure to develop the optimum properties can be reduced or even eliminated for some applications. Examples of suitable curing agents are: organic peroxides, such as benzoyl peroxide, and bis(a,a-dimethylbenzyl) peroxide; aliphatic polyamines, such as hexamethyienediamine, and tetraethylenepentamine; and derivatives of alphatic polyamines such as ethylenediamine carbamate, hexamethylenediamine carbamate, and N,N'-bis(arylalkylidene)alkylenediamines. Typical details of various methods of curing the known fiuoroelastomers are given in" the following references: U.S. Patents 2,951,832; 2,958,672; 2,965,553; 3,008,916; and 3,011,995. The following publications may also be consulted: Report No. 58-3, Viton A and Viton AHV, A. L. Moran and T. D. Eubank, Elastomer Chemicals Department, E. I. du Pont de Nemours and Co., Wilmington, Delaware, May 1958; and Report No. 59-4, Viton B, A. L. Moran, Elastomer Chemicals Department, E. I. du Pont de Nemours and Co., Wilmington, Delaware, October 1959.

The copolymers containing a pendant hydroxyl group may be cured by reacting them with organic polyisocyanates.

The copolymers of this invention may also be co-cured with known fluoroelastomers such as the copolymers of vinylidene fluoride and hexafiuoropropene or the copolymers of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene.

The copolymers of this invention have many uses. The cured copolymers are characterized by excellent oil resistance, good solvent resistance, good thermal stability, excellent resistance to ozone, excellent flame resistance, and good electrical properties. They may be employed in the preparation of tires, inner tubes, belts, hose and tubing, wire and cable jackets, footwear, sponges, coated fabrics, and a wide variety of coated or molded articles. They are particularly suitable for electrical applications where resistance to heat and solvents is needed, such as wire coatings for use in motors.

The following examples will better illustrate the nature of the present invention; however, the invention is not intended to be limited to these examples. Parts are by weight unless otherwise indicated.

EXAMPLES General procedure.The method used in the following examples, unless otherwise indicated, is as follows:

Part of the reaction mixture, as indicated in the examples is placed in a 400-milliliter s tainless steel shaker tube under nitrogen. The tube is cooled in a mixture of Dry Ice and acetone (about 78 C.), and is purged four times with nitrogen and vacuum, alternately, to remove air, the remainder of the polymerization system is then added and the tube is closed. The shaker tube is heated to the desired temperature with rapid agitation and is maintained at this temperature for the times indicated. The initial pressure at the operating temperature is usually 150-1000 p.s.i.g., and the pressure falls rapidly as the polymerization proceeds. The resultant latex is cooled in a mixture of Dry Ice and acetone and frozen solid and then warmed to room temperature, the supernatant fluid is removed by decantation, and the polymer is washed repeatedly with water in a Waring blender. The polymer is dried 'on a rubber mill at 100 C. Inherent viscosities are measured at 30 C. using a solution of 0.1 gram'of polymer in 100 milliliters of a solution consisting of 86 parts by weight of tetrahydrofuran and 14 parts by Weight N,N-dimethylformamide.

Unless otherwise stated, the compounding recipe used in curing the polymers is as follows:

The material is compounded by blending on a rubber mill.

Test pieces are cured in a mold in a press for one hour at 180 C. and are then postcured in an oven as indicated in the various examples.

The properties of the polymer are determined as follows:

The stress-strain data (modulus, tensile strength, elongation and permanent set) are obtained at C. using dumbbells 2.5 inches long and A inch wide at the narrowest section which are cut from a slab 0.04-0.05 inch thick. L1 Instron tensile testing machine, Model TT-B (Instron Engineering Corp.), is used at a cross-head speed of 10 inches per minute. The method followed is ASTM D 412-51 T. Yerzley resilience, hardness, and compression set are measured using pellets inch thick and 4 inch in diameter. The following methods are used:

Yerzley resilience ASTM D 945-59.

Compression set ASTM D 39555, Method B,

70 hours at 121 C.

Hardness, Shore A ASTM D 676-59 T.

In the tables shown below the following abbreviations are used:

M modulus at 100% elongation, p.s.i. T tensile strength at the break, p.s.i. E elongation at the break, percent Example 1 The initial charge added to the shaker tube'is a mixture consisting of:

Grams Potassium carbonate 4 2,2'-az0bis (Z-methylpropionitrile) 0.1 Tertiary butyl alcohol 156 2-chloroethyl vinyl ether 1.06

After cooling and removing air, the following are weighed in:

Grams Methyl vinyl ether 28 Tetrafluoroethylene 48 Analyses show the following:

Percent by weight C 36.5 H 4.0 Cl 0.65

The composition of the polymer is approximately 50 mole percent tetrafluoroethylene units, 49 mole percent methyl vinyl ether units, and 1 mole percent 2-chloroethyl vinyl ether units. 7

The polymer is compounded using the following recipe:

Parts by Weight Polymer 100 Medium thermal carbon black a- Magnesium oxide 15 Hexamethylenediamine carbamate 1.5

A slab is cured one hour at 170 C. in a press.

Table I shows the vulcanizate properties of the polymer prepared in this example (Polymer A) compared with those of a copolymer prepared in the same way as Polymer A except that it contained equimolar amounts of units of tetrafluoroethylene and methyl vinyl ether and no 2-chloroethyl vinyl ether (Polymer B).

TABLE I Polymer A Polymer B N 0 Post Cure- 460 290 1, 120 320 450 1, 000 Permanent Set, percent 400 After Post cure [or 2 days at 204 (3.:

100 l, 760 480 TB 2, 590 1, 020 En a 220 430 Permanent Set, percent 14 30 Example 2 The initial charge added to the shaker tube is a mixture consisting of:

Grams Potassium carbonate 4 2,2'-azobis(Z-methylpropionitrile) 0.1 Tertiary butyl alcohol 200 2-chloroethyl vinyl ether 6.4

7 After cooling and removing air, the following are weighed in:

Grams Methyl vinyl ether 26 Tetrafluoroethylene The shaker tube is heated to C. and is maintained at this temperature for 3 hours. The yield is 68 grams of a white, tough elastomer having an inherent viscosity of 1.02.

Analyses show the following: Percent by weight The polymer composition is approximately 50 mole percent tetrafluoroethylene units, 44 mole percent methyl vinyl ether units, and 6 mole percent 2-chloroethyl vinyl ether units.

The polymer is compounded using the following recipe:

Parts by weight Polymer Medium thermal carbon black 20 Magnesium oxide 15 Ethylenediamine carbamate 1.25

The compound is cured as described in Example 1. The properties are shown in Table II.

Hardness. Shore A Ycrzley Resilience, 25 C., percr Compression set, percent (701101 Example 3 The initial charge to the shaker tube is: Grams Ammonium persulfate 0.40 Sodium sulfite 0.10 Sodium lauryl sulfate 1.0 Water 175 Sodium carbonate 0.6 2-chloroethyl vinyl ether 11.7

After cooling and removing air, the following are weighed in:

Grams Methyl vinyl ether 26 Tetrafiuoroethylene 49 The polymerization is carried out for 2 hours at 50-60 C. The resulting latex is frozen solid in a Dry-Iceacetone bath (about 78 C.) and is then warmed to room temperature. The solid polymer is washed on a wash mill and is dried on a mill at 100 C. The yield is 72 grams of an attractive, strong elastomer having an inherent viscosity of 2.75. The elastomer cures satisfac- A copolymer is prepared as described above in the general procedure using the following ingredients:

Initial charge: Grams Potassium carbonate 4 2,2-azobis(Z-methylpropionitrile) 0.10

Tertiary butyl alcohol 156 2-iodoethyl vinyl ether 1.9 After cooling:

Methyl vinyl ether 29 Tetrafiuoroethylene The reaction is carried out at 75 C. for 3 hours. The yield is 60 grams of an elastomeric copolymer having an iodine content of. 1.6 percent and an inherent viscosity The. composition of the copolymer is approximately 50 mole percent tetrafluoroethylene units, 49 mole percent methyl vinyl ether units, and 1 mole percent 2-iodoethyl vinyl ether units.

When compounded, cured and tested as described in the above general procedure the elastomer has the following properties:

TABLE OF EXAMPLE 4 Postcurc at 201 C. None 6 hours 1 day 7 days 550 960 990 1. san 1, 470 2, 330 2, 420 2, 450

200 150 1' ill 5 5 Hardness, Sho e A 68 69 Ycrzley Resilience, 25 6., percent 35 27 Ycrzlcy Resilience, 100" (3.. percent S1 S4 Compression Set, percent (70 hours at 121 C.) 29 18 torily when compounded and cured as described above in Example 5 the general procedure. A i

copolymer is prepared as described in Example 3 The composition of the resulting copolymer 15 about above using thg following ingredients: 50 mole percent tetrafiuoroethylene units, 41 mole percent methyl vinyl ether units, and 9 mole percent 2-chlo- Imtlal Charge! Grams roethyl vinyl ether units. Potassium persulfate 0.40 E I 4 Sodium sulfite 0.08 mmpe Sodium lauryl sulfate 0.8 The substituted alkyl vinyl ether, 2-iodoethyl vinyl Sodium carbonate 0.6 ether, is prepared as follows: The following mixture is Water 200 refluxed for 5 hours at 86-89 C. Isopropyl alcohol 0.8 Grams 2-chloroethyl vinyl ether 2.1 Sodium sulfite 1 After cooling: 7 Sodium carbonate 1 Methyl vinyl ether 28 Sodium iodide 105 Tetrafiuoroethylene 50 0* g fi Z m ""351 The polymerization 1s carried out for 2 hours at 50-60" loroet yl vmyl et 61 C. The yield is grams of a tough elastomer which i To the reaction mixture is added 300 grams of water and 150 grams of chloroform. The lower layer is separated, washed with 10 percent potassium carbonate, and dried over anhydrous sodium sulfate.

On distillation there is obtained 33 grams of 2-chloroethyl vinyl ether (B.P. 26 C. at 20 mm. Hg) and 66 grams of 2-iodoethyl vinyl ether (B.P. 36 C. at 2 mm.

only 35 percent soluble in the tetrahydrofurandirnethylforrnamide solvent mixture. Analyses show the follow- Percent by weight Cl 0.9 F 45.2 C 37.8 H 3.7

9 The polymer composition is approximately 50 mole Initial charge: Grams percent tetrafluoroethylene units, 48 rnole percent methyl Isopropyl alcohol 0.8 vinyl ether units and 2 mole percent 2-chloroethyl vinyl Z-ethylhexyl vinyl ether 8.6 ether units. After cooling:

A white vulcanized elastomer is prepared by mixing 5 Methyl vinyl ether 31 the following on a rubber mill: Tetrafluoroethylene 50 Parts by weight Polymerization is carried out at 5060 C. for 2 hours. Copolymer 100 The yield is 69grams of an attractive elastomer having Magnesium oxide an inherent viscosity of 1.37. Analyses are 41.3% C, Titanium dioxide 4.3% H, and 0.8% Cl. The polymer composition is Hexamethylenediamine carbamate 1.25 10 approximately 50 mole percent tetrafluoroethylene units, 43 mole percent methyl vinyl ether units, 2 mole percent The cure is carried out in a press for 1 hour at 180 C. 2-chloroethyl vinyl ether units, and 5 mole percent 2- The table given below shows the properties of the cured ethylhexyl vinyl ether units.

TABLE OF EXAMPLE 5 Copolyrner of viuylidene fluoride and hexafluoro- Copolynler of this Example propene Postcure l (lay at 1 day at 1 day at 1 day at Color r 500 540 57 510 TB 2.100 2, 840 2, 560 2, 090 EB 260 300 250 270 Per 5 s 9 9 Hardness. Sher A. 63 64 G3 63 Yerzley Resilience, 0., percent 48 46 26 23 Compression Set, percent (70 hours at 121 C.) 32 18 9 1 Light tau. Brown. 3 White. 4 Very light ten.

copolymers and the properties of a vulcanizate prepared 35 The copolymer is cured as described above in the genin the same way from a commercially available copolymer of vinylidene fluoride and hexafluoropropene.

Example 6 A copolymer is prepared as described in Example 3 above using the following materials:

Initial charge: Grams Potassium carbonate 4 2,2-azobis(Z-methylpropionitrile) 0.10 Tertiary butyl alcohol 140 Ethyl vinyl ether 38.5

After cooling:

2-chloroethyl vinyl ether 2.1 Tetrafluoroethylene Example 7 A copolymer is prepared as described in Example 3 above using the following materials:

Initial charge; Grams Ammonium persulfate 0.34 Sodium sulfite 0.08 Sodium lauryl sulfate 1.0 Water 200 2-chloroethyl vinyl ether 2.1 Sodium carbonate 0.7

eral procedure. shown below:

The properties of the vulcanizate are Posteure None 1 clay at M m 270 610 Tn 1, 580 2, 440 En 440 230 Hardness, Shore A 57 60 Yerzley resilience, 25 0., percent 58 46 Yerzley resilience, 100 0., percent 63 87 Compression set, percent hours at 121 C.) 78 9 Brittle Po nt, 0 -48 Example 8 A copolymer is prepared as described in Example 3 above using the following materials:

Initial charge: Grams Ammonium persulfate 0.34 Sodium sulfite 0.08 Sodium lauryl sulfate 1.0 Isopropyl alcohol 0.8 Sodium carbonate 0.7

Water 200 IZ-chloroethyl vinylether 2.1

n-Butyl vinyl ether 11 After cooling:

Methyl vinyl ether 26 Tetrafiuoroethylene 5 O Example 9 A copolymer is prepared as described in Example 8 except that the monomers used are as follows:

Grams 2-chloroethyl vinyl ether 2.1 n-Butyl vinyl ether 27.5 Methyl vinyl ether 17 Tetrafluoroethylene 50 The yield is 56 grams of a copolymer having an inherent viscosity of 1.05.

The composition of the polymer is approximately 50 mole percent tetrafluoroethylene units, 24 mole percent of methyl vinyl ether units, 24 mole percent of butyl vinyl ether units, and 2 mole percent of 2-chloroethyl vinyl ether units.

The copolymer is cured as described above in the gen: eral procedure except that the amount of hexamethylenediamine carbamate used in the recipe is 0.75 part, and 0.75 part of azalamide (l,7-heptanedicarboxamide) is included in the recipe as an auxiliary curing agent. The properties of the vulcanizate are shown below:

Post/cure None 4 hours at M 190 250 Tn- 640 2, 570 E 1,000 3'20 Hardness, Shore A 52 45 Yerzley resilience, 25 0., percent 65 66 Yerzley resilience, 100 0., percent 78 Compression set, percent (70 hours at 121 0.)..- 100 39 Example 10 A copolymer is prepared as described in Example 8 except that the monomers used are as follows:

Grams 2-chloroethyl vinyl ether 2.1 Z-butoxyethyl vinyl ether 15. 8 Methyl vinyl ether 26 Tetrafluoroethylene The yield is 87 grams of a white elastomer which mills W611. Analyses are 41.1% C, 5.7% H, and 44.4% F.

The approximate polymer composition is 50 mole percent tetrafiuoroethylene units, 38 mole percent methyl vinyl ether units, 10 mole percent 2-butoxyethyl vinyl ether units, and 2 mole percent 2-chlor0ethyl vinyl ether units.

The elastomer is cured by the method of the general procedure with a postcure at 180 C. for 6 hours to give an elastomer with fair tensile properties, high resilience, and good low-temperature properties.

Example 11 A copolymer is prepared using the following materials:

Polymerization is carried out and the polymer is isolated as described in Example 3.

The yield is 64 grams of an elastomeric copolymer having an inherent viscosity of 1.99.

The composition of the polymer is approximately 50 mole percent tetrafiuoroethylene units, 46 mole percent methyl vinyl ether units, 2 mole percent l-isobutyl-3,5- dimethylhexyl vinyl ether units, and 2 mole percent 2- chloroethyl vinyl other units.

Example 12 Into a 400-millimeter silver-lined shaker tube under nitrogen is put:

Grams Sodium lauryl sulfate 1.0 2,2-azobis(Z-methylpropionitrile) 0.10

Sodium sulfite 0.5 Dibasic sodium phosphate (Na HPO 7H O) 1.0 2-formamidoethyl vinyl ether 2.2 Water 175 The tube is cooled in a Dry-Ice-acetone bath (-78 C.), evacuated, and 31 grams of methyl vinyl ether and 52 grams of tetrafluoroethylene are weighed in. The shaker tube is heated for 2 hours at C. The product is isolated by the method of Example 3 to give 77 grams of an elastomeric copolymer which handles well on a rubber mill.

Analyses are:

N (Kieldahl) percent 0.19 C do 39.0 H do 4.1 Inherent viscosity 1 1.4

1 Only 35% soluble.

The composition of the copolymer is approximately 50 mole percent tetrafiuoroethylene units, 49 mole percent methyl vinyl ether units, and 1 mole percent 2- formamidoethyl vinyl ether units.

The elastorner is cured by the method of the general procedure given above (Recipe A) and also by the following curing recipe (Recipe B) Parts by weight Copoly'mer Medium thermal carbon black 20 1,3-bis (hydroxyrnethyl Z-imidazolidone (dirnethylolethyleneurea) 3 Quinolinium tetrachlorozincate 0.5

The properties of the vulcanizate are shown below:

methyl vinyl ether, and tetrafiuoroethylene, as described below.

The initial charge to the shaker tube is:

Grams Ammonium persul'fate 0.40 Sodium sulfite 0.10 Sodium lauryl sulfate 1.0 Water 2-bromoethyl vinyl ether 2.8 Sodium carbonate 0.6

After cooling and removing air, the following are weighed in:

Grams Methyl vinyl ether Tetrafluoroethylene The polymerization is carried out for 2 hours at C. The product is isolated by the method of Example 3 and the yield is grams of an attractive strong elastomer. The elastomer cures satisfactorily when compounded and cured as described in the above general procedure.

The composition of the polymer is about 50 mole percent tetrafiuoroethylene units, 48 mole percent methyl vinyl ether units, and 2 mole percent 2-bromoethyl vinyl ether units.

Example 14 A copolymer is prepared from 2-hydroxyethyl vinyl ether, methyl vinyl ether, and tetrafluoroethylene, as described below. The initial charge to the shaker tube is exactly the same as in Example 13, except that 1.9 grams of 2hydroxylethyl vinyl ether is employed instead of 2.8 grams of 2-bromoethyl vinyl ether. The polymerization is carried out for 2 hours at 60 C. with a maximum pressure of 350 p.s.i.g. The product is isolated by the method of Example 3. The yield is grams of an attractive strong white elastomer, having the composition of about 50 mole percent tetrafluoroethylene units, 48 mole percent methyl vinyl ether units, and 2 mole percent 2-hydroxyethyl vinyl ether units.

141 The curing agents used and amounts by weight, per parts of copolymer are:

A. Z-mercapto-Z-imidazoline 0.5 B. Hexarnethylenediamine carbamate 1.5 C. Catechol 1.0 D. o-Aminophenol 1.0 E. Dimethylthiourea 1.0 F. None 1.0

Samples of the cured copolymers are immersed in acetone at room temperature and the percent gain in weight is measured after one day. T he results are as follows:

Samples: Percent weight gain A B 69 C 193 D 221 E 112 F 231 Example 16 Vinylidene- Copolymer hexafiuoro- Polyehloof Ex. 5 propane roprene copolymer Volume Resistivity, 0hn1-c1n 2.4X10 3.1)(10 X1 Dielectric constant at 1,000 cycles/second". 8. 9 1G. 9 7. 5 Power Factor, percent at 1,000 cycles/secon 2. 8 5 3 Dielectric strength, Volts/mil 531 258 500 Dielectric strength is measured by ASTM Method D 149-59 '1. Dielectric constant and power factor are measured by AS'IM Method D 150-59 T. Volume Resistivity is measured by ASTM Method D 257-58.

The following materials are mixed thoroughly on a rubber mill:

Parts by weight Copolymer of this example 100 Medium thermal carbon black 20 1,3-bis(3-isocyanato-4-methylphenyl)urea 1 Samples are cured one hour at C. in a press. Properties of the vulcanizate are:

Postcure None 1 day at 190 C.

Example 15 A copolymer of methyl vinyl ether, tetrafluoroethylene and 2-chloroethyl vinyl ether is prepared as described in Example 5. A masterbatch is prepared using the following recipe:

Parts by weight Copolymer of Example 5 100 Medium thermal carbon black 20 Magnesium oxide 5 Zinc oxide 5 Samples of this masterbatch are mixed With various curing agents and are cured in a press for 1 hour at 180 C. and postcured in an oven for 4 hours at 200 C.

Example 17 An elastomeric copolymer of the approximate composition 50 mole percent tetrafiuoroethylene units, 49.5 mole percent methyl vinyl ether units, and 0.5 mole percent 2-chloroethyl vinyl ether units is prepared as described below. The initial charge to the shaker tube is:

Grams Ammonium persulfate 0.40 Sodium sulfite 0.10 Sodium tetradecyl sulfate 0.75 Water Sodium bicarbonate 0.50 Sodium carbonate 0.10 2-chloroetl1yl vinyl ether 0.50

After cooling and removing air, the following are weighed in:

Methyl vinyl ether 32 Tetratluoroethylene 54 ethylenepentamine and the curing temperature is 160 C. The elastomer has the following properties:

Postcure None 20 hours at 193 C.

11 640 780 T .c 2, 300 2, 980 E3 310 250 units and mixtures of said units bearing different R radicals as defined hereinafter, wherein R is a member of the group consisting of a saturated aliphatic hydrocarbon radical containing 1 to 18 carbon atoms and the R'OCH CH radical where R is a saturated aliphatic hydrocarbon radical containing 1 to 4 carbon atoms and (c) about 0.2 to mole percent of -CHCI-I2 ()-CH2CH1-X units where X is a member of the group consisting of a halogen radical of an atomic number of 17 to 53, the hydroxyl group and a o NH%Y radical where Y is a member of the group consisting of hydrogen and a saturated aliphatic hydrocarbon radical containing 1 to 8 carbon atoms.

2. A curable elastomeric copolymer as defined in claim 1 where said R is methyl.

3. A curable elastomeric copolymer as defined in claim 1 where said X is a halogen of atomic number 17-53.

4. A curable elastomeric copolymer as defined in claim 1 where R is a saturated aliphatic hydrocarbon radical containing 3 to 18 carbon atoms in about 5 to about mole percent of said (b) units and in the remainder of said (b) units R is methyl.

5. A curable elastomeric copolymer as defined in claim 1 where said (c) units are present in about 0.5 to 4 mole percent.

6. A curable elastomeric copolymer as defined in claim 1 Where said X is chlorine.

7. A curable elastomeric copolymer as defined in claim 1 where said X is bromine.

8. A copolymer as defined in claim 1 which has been cured.

9. A cured elastomeric copolymer obtained by mixing a member of the group consisting of hexamethylenediamine carbamate and ethylenediamine carbamate and the curable copolymer of claim 1 wherein X is a halogen radical of atomic number of 17 to 53 and heating said mixture.

10. A cured elastomeric copolymer obtained by mixing hexamethylenediamine carbamate and the curable copolymer of claim 1 wherein X is chlorine and heating said mixture.

11. A cured elastomeric copolymer obtained by mixing an organic polyisocyanate and the curable copolymer of claim 1 wherein X is the hydroxyl group and heating said. mixture.

12. A curable elastomeric copolymer comprising (a) about 50 mole percent of CF --CF units, (b) about to 49.5 mole percent of units selected from the group consisting of units and mixtures of said units bearing different R radicals as defined hereinafter, R being a member of the group consisting of a hydrocarbon radical containing 1 to 18 carbon atoms and the ROCH CH radical where R is a saturated aliphatic hydrocarbon radical containing 1 to 4 carbon atoms and (c) about 0.5 to 10 mole percent of units where X is a member of the group consisting of a halogen radical of an atomic number of 17 to 53, the hydroxyl group and a o NHi J-Y V radical where Y is a member of the group consisting of hydrogen and a saturated aliphatic hydrocarbon radical containing 1 to 8 carbon atoms.

13. A curable elastomeric copolymer as defined in claim 12 where said R is methyl.

14. A curable elastomeric copolymer as defined in claim 13 where said (c) units are present in about 0.5 to 4 mole percent.

15. A curable elastomeric copolymer as defined in claim 12 where X is chlorine and where R is methyl.

16. A curable elastomeric copolymer as defined in claim 12 where X is bromine.

17. A curable elastomeric copolymer as defined in claim 12 where R is a saturated aliphatic hydrocarbon radical containing 3 to 18 carbon atoms in about 5 to about 20 mole percent of said (b) units and in the remainder of said (b) units R is methyl.

18. A copolymer as defined in claim 12 which has been cured.

References Cited by the Examiner UNITED STATES PATENTS 2,468,664 4/1949 Hanford et al 26087.5 2,727,020 12/1955 Melarned 260-803 2,779,025 1/1957 Perry 26087.5 2,834,767 5/1958 Hoyt 26O87.5 2,871,203 1/1959 Melamed 26087.5 2,975,164 3/1961 Crawford 26088.1 2,991,278 7/1961 Schildknecht 260-80.7 3,163,628 12/1964 Bolstad 260-87.5 3,171,830 3/1965 Kehr 260-88.2 3,235,537 2/1966 Albin et al 26080.5

LEGN I. BERCOVITZ, Primary Examiner.

DONALD E. CZAJ A, Examiner.

M. C. JACOBS, F. MCKELVEY, Assistant Examiners. 

1. A CURABLE ELASTOMERIC COPOLYMER COMPRISING (A) ABOUT 45 TO 55 MOLE PERCENT OF -CH2-CH2- UNITS, (B) ABOUT 54.8 TO 35 MOLE PERCENT OF UNITS SELECTED FROM THE GROUP CONSISTING OF
 11. A CURED ELASTOMERIC COPOLYMER OBTAINED BY MIXING AN ORGANIC POLYISOCYANATE AND THE CURABLE COPOLYMER OF CLAIM 1 WHEREIN X IS THE HYDROXYL GROUP AND HEATING SAID MIXTURE. 